Electrostatic interaction systems and methods thereof

ABSTRACT

An electrostatic interaction system includes a first structure having a first fixed electrostatic charge and a second structure having a second fixed electrostatic charge. The polarity of the first and second fixed electrostatic charges determines a positional relationship of the first structure to the second structure.

[0001] The present invention claims the benefit of U.S. ProvisionalPatent Application Serial No. 60/297,327, filed Jun. 11, 2001, which ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] This invention relates to electrostatic devices and a methodsand, more particularly, to electrostatic levitation and attractionsystems and methods thereof.

BACKGROUND OF THE INVENTION

[0003] In the macroscopic realm, there is often an undesirablerestriction of the relative movement between two surfaces. This tendencyof two surfaces to stick to each other is called friction and can besignificantly reduced by introducing an intermediate material, i.e. alubricant, that is slippery between the surfaces.

[0004] In the microscopic realm, there also is an undesirablerestriction of the relative movement between two surfaces.Unfortunately, unlike the macroscopic realm, the introduction of anintermediate material between the surfaces may actually increase thepropensity of micro components to stick together. Furthermore, in themicro and nano realms short-range forces, such as the van der Waals andelectrostatic forces, become extremely important and often lead toserious limitations in the overall design and miniaturization ofcomponents. This effect is often referred to as stiction.

SUMMARY OF THE INVENTION

[0005] An electrostatic interaction system in accordance with oneembodiment of the present invention includes a first structure having afirst fixed electrostatic charge and a second structure having a secondfixed electrostatic charge. The polarity of the first and second fixedelectrostatic charges determines a positional relationship of the firststructure to the second structure.

[0006] A method for making an electrostatic interaction system inaccordance with another embodiment of the present invention includesproviding a first structure having a first fixed electrostatic chargeand providing a second structure having a second fixed electrostaticcharge. The polarity of the first and second fixed electrostatic chargesdetermines a positional relationship of the first structure to thesecond structure.

[0007] An electrostatic levitation system in accordance with anotherembodiment of the present invention includes a first structure having afirst fixed electrostatic charge and a second structure having a secondfixed electrostatic charge. The polarity of the first and second fixedelectrostatic charges is the same and holds the first and secondstructures in a spaced apart positional relationship.

[0008] An electrostatic attraction system in accordance with anotherembodiment of the present invention includes a first structure having afirst fixed electrostatic charge and a second structure having a secondfixed electrostatic charge. The polarity of the first and second fixedelectrostatic charges is opposite which attracts and holds the first andsecond structures together.

[0009] The present invention provides an electrostatic levitation systemthat has a compensating force that is sufficient to keep microcomponents from actually coming within the short-range distances fromeach other. This technique provides levitation without using magnetism.The present application has a variety of applications includingelectrostatic bearings. One of the features of the invention is the useof imbedded repulsive electrostatic forces to overcome stiction.

[0010] The present invention also provides an electrostatic attractionsystem that has a complementary force that is sufficient to attractcomponents to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGS. 1-6 are cross-sectional view of a method of making anelectrostatic levitation system in accordance with one embodiment of thepresent invention;

[0012]FIG. 7 is a cross-sectional view of an electrostatic levitationsystem in accordance with another embodiment of the present invention;and

[0013]FIG. 8 is a cross-sectional view of an electrostatic attractionsystem in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION

[0014] Electrostatic interaction systems 10(l)-10(3) in accordance withembodiments of the present invention are illustrated in FIGS. 6-8. Theelectrostatic interaction systems 10(1)-10(3) each include a firststructure 12 having a first fixed electrostatic charge 14 and a secondstructure 16(1), 16(2), or 16(3) having a second fixed electrostaticcharge 18. The polarity of the first and second fixed electrostaticcharges 14 and 18 determines a positional relationship of the firststructure 12 to the second structure 16(1), 16(2), or 16(3). The presentinvention provides electrostatic interaction systems, such aselectrostatic levitation systems 10(1) and 10(2) and electrostaticattraction systems 10(3), for microscopic environments.

[0015] Referring to FIG. 6, an electrostatic levitation system 10(1) inaccordance with one embodiment is illustrated. The system 10(1) mayinclude a housing 20 for the first and second structures 12 and 16(1). Avariety of different types of housings, such as a bearing case, with avariety of different configurations can be used.

[0016] The first structure 16(1) includes a first insulating layer 22,such as SiO₂, located on a second insulating layer 26, such as Si₃N₄,although other materials and other numbers of layers could be used. Afirst interface 24 is located between the first and second insulatinglayers 22 and 26 and the first fixed electrostatic charge 14 having anegative polarity is stored at the first interface 24, although thefirst fixed electrostatic charge 14 could have a positive polarity anddepending on the number of layers, the first structure 12 can have moreinterfaces where fixed electrostatic charge can be stored. Although afirst structure 12 made of first and second insulating layers 22 and 26is shown, other types of members which can hold a fixed charge can alsobe used, such as an electret. The first stored fixed electrostaticcharge 14 has a magnitude of at least 1×10¹² charges per cm², althoughthe magnitude can vary depending on the application.

[0017] An optional first component 28, such as a machine part, isconnected to the first insulating layer 22, although other types offirst components can be used. The first component 28 is made of aconductive material, such as poly silicon, although other types ofmaterials, such as an insulating material, can be used. If firstcomponent 28 is made of an insulating material, then other techniquesfor imbedding the fixed charge in the interface 24 may be used, such asusing an electron gun.

[0018] The second structure 16(1) includes a third insulating layer 30,such as Si₃N₄, located on a fourth insulating layer 32, such as SiO₂,although other materials and other numbers of layers could be used. Asecond interface 34 is located at the interface between the third andfourth insulating layers 30 and 32 and the second fixed electrostaticcharge 18 also having a negative polarity is stored at the secondinterface 34, although the second fixed electrostatic charge 18 couldhave a positive polarity and depending on the number of layers, thesecond structure 16(1) can have more interfaces where fixedelectrostatic charge can be stored. Although a second structure 16(1)made of first and second insulating layers 30 and 32 is shown, othertypes of members which can hold a fixed charge can also be used, such asan electret. The second stored fixed electrostatic charge 18 has amagnitude of 1×10¹² charges per cm², although the magnitude can varydepending on the application.

[0019] An optional second component 36, such as a machine part, isconnected to the fourth insulating layer 32, although other types ofsecond components can be used. The second component 36 is made of aconductive material, such as poly silicon, although other types ofmaterials, such as an insulating material, can be used. If secondcomponent 36 is made of an insulating material, then other techniquesfor imbedding the fixed charge in the interface 34 may be used, such asusing an electron gun.

[0020] If the first and second stored fixed electrostatic charges 14 and18 in the first and second structures 12 and 16(1) have the samepolarity or sign, then an electrostatic repulsion force results which issufficient to keep the two structures 12 and 16(1) in a spaced apartrelation with each other. If the housing 20 is included it provides acasing to hold the first and second structures 12 and 16(1) in theirspaced apart relation to each other. This embodiment mitigates ofsliding friction and the short range stiction.

[0021] Referring to FIG. 7, an electrostatic levitation system 10(2) inaccordance with another embodiment is illustrated. The electrostaticlevitation system 10(2) is the same as the electrostatic levitationsystem 10(1) shown in FIG. 6, except as described below. Elements inFIG. 7 which are identical to those elements in FIG. 6 have likereference numerals. In this particular embodiment, the second structure16(2) is an electret, such as a polymer with residual polarizationcharge, with a second stored fixed electrostatic charge 18, althoughother types of members which can hold a fixed charge can be used.Additionally, in this particular embodiment a second component 36 is notconnected to the second structure 16(2), although other configurationsare possible, such as having a second component 36 connected to thesecond structure 16(2), but not having a first component 28 connected tothe first structure 12.

[0022] Referring to FIG. 8, an electrostatic attraction system 10(3) inaccordance with another embodiment is illustrated. The electrostaticattraction system 10(3) is the same as the electrostatic levitationsystem 10(1) shown in FIG. 6, except as described below. Elements inFIG. 8 which are identical to those elements in FIG. 6 have likereference numerals. In this particular embodiment, the first structure12 has a first a fixed electrostatic charge 14 with a negative polarityand the second structure 16(3) has a second fixed electrostatic charge18 with a positive polarity, although other arrangements are possible,such as the first structure 12 having a first a fixed electrostaticcharge 14 with a positive polarity and the second structure 16(3) havinga second electrostatic fixed charge 18 with a negative polarity. Anotherpossible arrangement is a fixed charge in one of the first and secondstructures and an induced charge in the other one of the first andsecond structures which will result in an electrostatic attraction forceto keep the first and second structures together.

[0023] If the first and second stored fixed electrostatic charges 14 and18 in the first and second structures 12 and 16(3) have the oppositepolarity or sign, then an electrostatic attraction force results whichis sufficient to keep the two structures 12 and 16(3) together.

[0024] A method for making an electrostatic levitation system 10(1) inaccordance with one embodiment is shown in FIGS. 1-6. Referring to FIG.1, an insulating layer 22, such as SiO₂, is deposited on the firstcomponent 28, such as Si, and another insulating layer 26, such asSi₃N₄, is deposited on the insulating layer 22 to form a member with ahigh density of electronic charge traps at an interface 24 betweenlayers 22 and 26, although other numbers of layers could be deposited,other materials could be used for each of the layers, and other types ofmembers, such as a dual insulator graded interface, multiple deltalayered interface, or an electret, could be used in place of insulatinglayers 22 and 26.

[0025] Referring to FIG. 2, a sacrificial conducting layer 38, such aspoly silicon, is deposited on the insulating layer 26, although othertypes of materials could be used for layer 38.

[0026] Referring to FIG. 3, an insulating layer 30 is deposited on thesacrificial conducting layer 38, such as Si₃N₄, and another insulatinglayer 32 is deposited on the insulating layer 30, such as SiO₂, to forma member with a high density of electronic charge traps at an interface34 between layers 30 and 32, although other numbers of layers could bedeposited, other materials could be used for each of the layers, andother types of members with a fixed electrostatic charge, such as anelectret, could be used in place of insulating layers 30 and 32.

[0027] Referring to FIG. 4, a second component 36, such as Si, isconnected to the insulating layer 32, although other types of materialscould be used. For example, the second component 36 may be a conductingsacrificial layer which is subsequently removed using standard removalprocedures for sacrificial layers, such as by chemical etching.

[0028] Referring to FIG. 5, an electrical bias from a power supply 42 isapplied between the first component 28 and the sacrificial conductinglayer 38 to cause electrons to be injected into the first structure 12.This in turn will cause electrons to be trapped at interface 24 betweenlayers 22 and 26, although other techniques for injecting the electronsinto the interface 24 could be used, such as using an electron gun orequilibrium charge from processing. Although the injection of electronsinto the interface 24 is shown, other techniques can also be used, suchas the extraction of electrons from the interface 24 to leave a netpositive charge, i.e. hole injection, at the interface 24. Typically,higher charge levels can be obtained for the trapped electron case.

[0029] An electrical bias from a power supply 40 is also applied betweenthe sacrificial conducting layer 38 and the second component 36, causingelectrons to be trapped at the interface 34, although other techniquesfor injecting the electrons into the interface 34 could be used, such asusing an electron gun or equilibrium charge from processing. Althoughthe injection of electrons into the interface 34 is shown, othertechniques can also be used, such as the extraction of electrons fromthe interface 34 to leave a net positive charge, i.e. hole injection, atthe interface 34. Typically, higher charge levels can be obtained forthe trapped electron case.

[0030] Referring to FIG. 6, once the fixed electrostatic charge 14 and18 at the interfaces 24 and 34 has been obtained, the sacrificial layer38 is removed. A variety of techniques for removing the sacrificiallayer 38 can be used, such as by chemical etching. Again, the secondcomponent 36 may be a conducting sacrificial layer and subsequently beremoved by standard process procedures at this time. The resulting firstand second components 28 and 36 are held in a spaced apart relation byrepulsive electrostatic forces from the fixed electrostatic charges 14and 18 at the interfaces 24 and 34.

[0031] Referring to FIG. 7, the method for making the electrostaticlevitation system 10(2) is the same as shown and described for makingelectrostatic levitation system 10(1), except that second structure16(1) with insulating layers 30 and 32 is replaced with another secondstructure 16(2) which is an electret, although other members which canhold a fixed charge can be used for second structure 16(2) and for firststructure 12.

[0032] Referring to FIG. 8, the method for making the electrostaticattraction system 10(3) is the same as shown and described withreference to FIGS. 1-6 for making electrostatic levitation system 10(1),except that the obtained fixed electrostatic charges 14 and 18 in theinterfaces 24 and 34 is opposite to attract the structures 12 and 16(3)together. In this embodiment, electrons are injected into interface 24and electrons are extracted from interface 34 to create the attractionforce, although other arrangements can be used.

[0033] Having thus described the basic concept of the invention, it willbe rather apparent to those skilled in the art that the foregoingdetailed disclosure is intended to be presented by way of example only,and is not limiting. Various alterations, improvements, andmodifications will occur and are intended to those skilled in the art,though not expressly stated herein. These alterations, improvements, andmodifications are intended to be suggested hereby, and are within thespirit and scope of the invention. Additionally, the recited order ofprocessing elements or sequences, or the use of numbers, letters, orother designations therefor, is not intended to limit the claimedprocesses to any order except as may be specified in the claims.Accordingly, the invention is limited only by the following claims andequivalents thereto.

What is claimed is:
 1. An electrostatic interaction system comprising: afirst structure having a first fixed electrostatic charge; and a secondstructure having a second fixed electrostatic charge, wherein a polarityof the first and second fixed electrostatic charges determines apositional relationship of the first structure to the second structure.2. The system as set forth in claim 1 wherein the polarity of the firstand second fixed electrostatic charges is the same and holds the firstand second structures in a spaced apart positional relationship witheach other.
 3. The system as set forth in claim 1 wherein the polarityof the first and second fixed electrostatic charges is opposite andattracts and holds the first and second structures together.
 4. Thesystem as set forth in claim 1 wherein at least one of the first andsecond structures comprises at least a first insulating layer on asecond insulating layer, a first interface is located at a junctionbetween the first and second insulating layers and one of the first andsecond fixed electrostatic charges is stored at the first interface. 5.The system as set forth in claim 1 wherein at least one of the first andsecond structures comprises an electret which stores one of the firstand second fixed electrostatic charges.
 6. The system as set forth inclaim 1 further comprising at least one component connected to one ofthe first and second structures.
 7. The system as set forth in claim 1further comprising a housing, the first and second structures located inat least a portion of the housing.
 8. A method for making anelectrostatic interaction system, the method comprising: providing afirst structure having a first fixed electrostatic charge; and providinga second structure having a second fixed electrostatic charge, wherein apolarity of the first and second fixed electrostatic charges determinesa positional relationship of the first structure to the secondstructure.
 9. The method as set forth in claim 8 wherein the polarity ofthe first and second fixed electrostatic charges is the same and holdsthe first and second structures in a spaced apart positionalrelationship with each other.
 10. The method as set forth in claim 8wherein the polarity of the first and second fixed electrostatic chargesis opposite and attracts the first and second structures together. 11.The method as set forth in claim 8 further comprising providing at leasta first component which is connected to one of the first and secondstructures.
 12. The method as set forth in claim 11 wherein theproviding the first structure further comprises: depositing a firstinsulating layer on the first component, at least a portion of the firstcomponent is made of a conductive material; depositing at least a secondinsulating layer on the first insulating layer, a first interface islocated at a junction between the first and second insulating layers;and depositing a sacrificial layer on the second insulating layer, atleast a portion of the sacrificial layer is made of a conductivematerial.
 13. The method as set forth in claim 12 further comprising:depositing a third insulating layer on the sacrificial layer; anddepositing a fourth insulating layer on the third insulating layer, asecond interface is located at a junction between the third and fourthinsulating layers.
 14. The method as set forth in claim 13 furthercomprising connecting a second component to the fourth insulatingmaterial, at least a portion of the second component made of aconductive material.
 15. The method as set forth in claim 14 furthercomprising: applying a first electrical bias between the sacrificiallayer and the first component to inject the first fixed electrostaticcharge; and applying a second electrical bias between the sacrificiallayer and the second component to inject the second fixed electrostaticcharge.
 16. The method as set forth in claim 15 further comprisingremoving the sacrificial layer.
 17. The method as set forth in claim 15wherein a polarity of the first and second electrical biases is thesame.
 18. The method as set forth in claim 15 wherein a polarity of thefirst and second electrical biases is opposite.
 19. The method as setforth in claim 8 wherein at least one of the first and second structurescomprises an electret which stores one of the first and second fixedelectrostatic charges.
 20. The system as set forth in claim 8 furthercomprising providing a housing, the first and second structures locatedin at least a portion of the housing.
 21. An electrostatic levitationsystem comprising: a first structure having a first fixed electrostaticcharge; and a second structure having a second fixed electrostaticcharge, wherein a polarity of the first and second fixed electrostaticcharges is the same and holds the first and second structures in aspaced apart positional relationship.
 22. The system as set forth inclaim 21 wherein at least one of the first and second structurescomprises at least a first insulating layer on a second insulatinglayer, a first interface is located at a junction between the first andsecond insulating layers and one of the first and second fixedelectrostatic charges is stored at the first interface.
 23. The systemas set forth in claim 21 wherein at least one of the first and secondstructures comprises an electret which stores one of the first andsecond fixed electrostatic charges.
 24. The system as set forth in claim21 further comprising at least one component connected to one of thefirst and second structures.
 25. The system as set forth in claim 21further comprising a housing, the first and second structures located inat least a portion of the housing.
 26. An electrostatic attractionsystem comprising: a first structure having a first fixed electrostaticcharge; and a second structure having a second fixed electrostaticcharge, wherein a polarity of the first and second fixed electrostaticcharges is opposite which attracts and holds the first and secondstructures together.
 27. The system as set forth in claim 26 wherein atleast one of the first and second structures comprises at least a firstinsulating layer on a second insulating layer, a first interface islocated at a junction between the first and second insulating layers andone of the first and second fixed electrostatic charges is stored at thefirst interface.
 28. The system as set forth in claim 26 wherein atleast one of the first and second structures comprises an electret whichstores one of the first and second fixed electrostatic charges.
 29. Thesystem as set forth in claim 26 further comprising at least onecomponent connected to one of the first and second structures.
 30. Thesystem as set forth in claim 26 further comprising a housing, at leastone of the first and second structures located in at least a portion ofthe housing.